Unified Valence Bond Theory of Electronic Structure: Applications

ISBN-13: 9783540120001 / Angielski / Miękka / 1983 / 589 str.

N. D. Epiotis

Opis

The bond diagrammatic representation of molecules is the foundation of MOVB theory. To a certain extent, this kind of representation is analogous to the one on which "resonance theory" is based and this fact can be projected by a comparison of the various ways in which MOVB theory depicts a species made up of three core and two ligand MO's which define two subsystems containing a total of six electrons and the ways in which "resonance theory" (i. e., qualitative VB theory) depicts a six-electron-six-AO species such as the pi system of CH =CH-CH=CH-CH=O. The 2 different pictorial representations are shown in Scheme 1 so that the analogies are made evident. First of all, the total MOVB diagrammatic representation of the 6/5 species is obtained by a linear combination of three complete bond diagrams, as in Al, which describe the optimal linear combination of l MOVB Configuration Wavefunctions (CW's). By the same token, a total VB diagrammatic representation of the 6/6 species can be obtained by writing a "dot structure," as in Bl, and taking this to mean the optimal linear combination of all VB CW's. Next, we can approxi- mate the MOVB wavefunction of the 6/5 species by one complete (or detailed) bond dia- gram" (A2). No simple VB representation analogy can be given in this case. Alterna- tively, we can approximate the MOVB wavefunction by a linear combination of compact bond diagrams, as in A3, in the way described before.

Spis treści

One. The Conceptual Power of Molecular Orbital Valence Bond (MOVB) Theory.- 1. The Induced Deexcitation Model.- 2. Why do Organolithium Monomers have Strange Structures?.- 3. The Molecular Orbital-Valence Bond Theory of Excited States.- 4. The “Forbidden” World of Chemistry.- 5. The Concept of Natural Ligand Nonbonded Repulsion. The Ethane Paradigm.- 6. Conformational Isomerism of N2H4 and Derivatives. The Stereochemical Consequences of “Forbiddenness” Removal.- 7. Geometric Isomerism: The Simplest Illustrator of Orbital Symmetry Control of Molecular Stereochemistry.- 8. Structural Isomerism and the Electronic Basis for Ligand Segregation on C2 Cores.- 9. The Saga of “Hypervalent” Molecules.- 10. The Molecular Orbital-Valence Bond Theory of Inorganic Chemistry.- 11. How to build Bridges by Molecular Orbital-Valence Bond Theory: The Structures of A2X4 Molecules.- 12. Why Benzene prefers to substitute and an Olefin ilikes to add?.- 13. Why “Effective” Bonds exist when “Real” Bonds are Absent: The Electronic Structure of the (1.1.1.) Propellane.- 14. The Detailed Electronic Structure of Carbocyclic Molecules and the Concept of Superaromaticity.- 15. The Explicit Theory of “Real” Electrocyclizations of Closed and Open Shell Molecules.- Two. Beyond Monodeterminantal MO Theory.- 16. Frontier Configurations and a New Classification of Annulenes.- 17. Frontier Configuration Theory of Spin Selection.- 18. Why a Net Bond exists when it appears to be Nonexistent: The Electronic Structures of F2 and Inert Gas Fluorides.- 19. Chemical Anticooperativity and Sigma-Pi Hybridization.- 20. The Stereochemical Consequences of Coulomb Polarization in Ground State Molecules.- 21. The Qualitative Rationalization and Prediction of “Correlation Effects” in “Complex” Ground State Molecules.- Epilogue.- Erratum.